Construction machine

ABSTRACT

A rear half part of a surface of a main body of a working oil tank installed in line with a control valve opposing to the valve is dented in an inclining surface shape in the direction moving away from the valve so that between both the tank and the valve, is formed a working space for attaching and detaching a pressure compensating spool, while return tubes are separately connected to the upper and the lower side of a filter case side wall within the body. Within the body, is provided a cylindrical filter case having a bottom in which a return filter for return oil is housed, and the return tubes are connected to the case side wall in a state of communicating with the inside of the filter case. In this configuration, a filter receiving plate is provided in a lower part within the filter case with leaving a gap between the plate and the filter case bottom wall in a state that the plate is supported by a return pipe, the return filter is disposed on the plate, and the return tubes are connected to the filter case side wall on the lower side than the plate.

This application is a divisional of application Ser. No. 11/931,350,filed on Oct. 31, 2007, the entire contents of which are incorporatedherein by reference. U.S. Ser. No. 11/931,350 claims priority under 35U.S.C. 119 to Japanese Applications 2006-311719 and 2006-311720 bothfiled on Nov. 17, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a construction machine provided with aworking oil tank such as a hydraulic excavator.

2. Description of the Related Art

THE RELATED ART will be described taking a hydraulic excavator of apreferred example of the present invention as an example.

The hydraulic excavator is, as shown in FIG. 5, formed by rotatablymounting an upper rotating body 2 on a crawler type lower traveling body1 and attaching a working attachment 3 to the upper rotating body 2.

The working attachment 3 is formed by a boom 4 freely raising andlowering, an arm 5 attached to an front end of the boom 4, a bucket 6attached to a front end of the arm 5, a boom cylinder 7, an arm cylinder8 and a bucket cylinder 9 serving as hydraulic actuators for driving theboom, the arm and the bucket.

FIG. 6 shows device arrangement of a part of the upper rotating body 2,and FIG. 7 is an enlarged view of a part of FIG. 6.

An engine 10 serving as a power source and a hydraulic pump 11 servingas a hydraulic source are installed in a rear part of an upper frame 12serving as a base of the upper rotating body 2. On one of left and rightsides (on the right side in an example of the figure) on the front sideof the engine 10 and the hydraulic pump 11, are installed and laterallyaligned a control valve 13 for controlling an action of the hydraulicactuator such as each of the hydraulic cylinders 7 to 9, and a workingoil tank 14 for supplying working oil to the hydraulic actuator, withthe control valve being placed on the outer side.

It should be noted that a guard cover 15 is openably attached to an endon the right side of the upper frame taking the front side as center. Byopening the guard cover 15, maintenance of the control valve 13 isperformed.

The control valve 13 is, as shown in FIG. 7, formed such that aplurality of main spools (one main spool is shown in the figure) 16 forcontrolling the working direction and speed on the basis of a leveroperation for each actuator are built in one valve block 17 in a storyshape.

In the control valve 13, the main spools 16 are provided in parallelwith the working oil tank 14, that is, in the longitudinal direction,due to tube connection to each port or the like.

When there is a need for a so-called pressure compensating function forcompensating an action pressure of the hydraulic actuator and ensuring afixed operability irrespective of a change in load, a pressurecompensating spool (also called as load sensing spool) 18 is provided atright angles with the main spool 16, that is, in the lateral direction.

In FIG. 7, the reference numeral 19 denotes a bolt for closing a take-inand take-out port for the pressure compensating spool 18. At the time ofassembling a valve and at the time of maintenance, the pressurecompensating spool 18 is attached to and detached from the valve block17 in a state that the bolt 19 is removed.

Meanwhile, a configuration the working oil tank 14 as THE RELATED ART isshown in FIGS. 8 and 9.

The working oil tank 14 is formed such that a cylindrical filter case 21having a bottom is attached within a tank main body 20, a return filter22 is housed inside thereof, and return oil flowing from the hydraulicactuator through a plurality of return tubes 23 is filtered in thereturn filter 22, and then returned to the inside of the tank main body20 by a return pipe 24 installed through a central part of a filter casebottom wall 21 a.

The return filter 22 is disposed on the bottom wall 21 a of the filtercase 21 and held by a push spring 25.

In the figure, the reference numeral 26 denotes a suction filter forfiltering feed oil and the reference numeral 27 denotes a suction tube.

In the tank structure, as THE RELATED ART, all the return tubes 23 areconnected to the upper side than the return filter 22, that is, to anupper part of a filter case side wall 21 b.

In the above configuration, a point that the control valve 13 and theworking oil tank 14 are aligned is shown in Japanese Patent Laid-OpenNo. Hei11-190449, a control valve structure including the pressurecompensating spool 18 is shown in Japanese Patent Laid-Open No.2002-13656, and a configuration of the working oil tank 14 is shown inJapanese Patent Laid-Open No. 2005-282805.

When taking a device layout shown in FIGS. 6 and 7, at the time ofmaintenance of the control valve 13, the main spool 16 is easilyattached and detached in the longitudinal direction due to spaces onboth the front side and the rear side. However, since a left side spaceS which is on the working side for performing attachment and detachmentof the pressure compensating spool 18 is closed by the working oil tank14, it is difficult or impossible to perform an attachment anddetachment work of the pressure compensating spool 18.

Therefore, at the time of maintenance, the entire control valve 13 hasto be removed from the upper frame 12, and hence the work is verytroublesome.

As countermeasures thereof, it is thought that (A) the working oil tank14 is displaced to the inner side (the left side) and a sufficientworking space is ensured between the working oil tank 14 and the controlvalve 13, and (B) the working oil tank 14 is downsized in the lateraldirection.

However, it is difficult to realize the countermeasure (A) since in thehydraulic excavator, particularly a small excavator of small rotatingtype or the like, a device installation space is limited or the like.

It is also difficult to realize the countermeasure (B), since a tankcapacity of the working oil tank 14 is decreased so that it is notpossible to ensure a necessary amount of working oil.

It should be noted that a return structure of the filter case 21 or thelike shown in FIGS. 8 and 9 is downsized (reduced in diameter) so thatan effective capacity of the tank main body 20 is increased and hencethe tank is downsized.

However, in the working oil tank 14 mentioned above, all the returntubes 23 are concentrated on and connected to the upper part of the sidewall 21 of the filter case in an octopus shape. Therefore, in order toensure a tube connection area, a perimeter of the filter case 21 has tobe large. As a result, it is substantially impossible to reduce thediameter of the filter case 21, and hence it is actually difficult todownsize the tank.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a constructionmachine capable of downsizing a working oil tank so as to ensure asufficient working space for attaching and detaching a spool between theworking oil tank and a control valve and also ensuring a necessary tankcapacity under the condition that the control valve and the working oiltank are installed in line with each other and a part disturbed by atank at the time of attachment and detachment thereof (a pressurecompensating spool in the above example) is built in the control valve,or a construction machine provided with a working oil tank capable ofavoiding direct contact of return oil with a side surface of a filter,separately connecting return tubes to a filter case and easingrestrictions on a combination of the return tubes so as to simplify aconnection structure.

Firstly, the construction machine according to the present invention hasthe following basic configuration.

The present invention is a construction machine, comprising a controlvalve for controlling an action of a hydraulic actuator, a working oiltank installed in line with the control valve, a filter case in which areturn filter for filtering return oil is housed, the filter case beingprovided within a tank main body of the working oil tank, and aplurality of return tubes connected to a filter case side wall, whereina surface of the tank main body of the working oil tank opposing to thecontrol valve is inwardly dented so that between both the working oiltank and the control valve, is formed a working space which is necessaryfor attaching and detaching a part of the control valve, while thereturn tubes are separately connected to the upper side and the lowerside of the filter case side wall.

According to the present invention, the surface of the tank main body ofthe working oil tank opposing to the valve is inwardly dented so thatbetween the tank and the control valve, is formed a working space whichis necessary for attaching and detaching a part of the control valve.Therefore, it is possible to easily attach and detach the object partdue to the working space.

Further, since the return tubes are separately connected to the upperside and the lower side of the filter case, the filter case is downsized(reduced in diameter) so that an effective capacity of the tank mainbody is increased. Therefore, it is possible to cover the surfaceopposing to the valve which is dented in order to ensure the workingspace so as to ensure a necessary tank capacity.

The return tubes are separated to the upper side and the lower side sothat the restrictions on a combination of the return tubes are eased.Therefore, a shape of the return tubes and the connection structure aresimplified and it is advantageous in terms of a manufacturing propertyand cost. An effect at this point is remarkable in a small tank mountedin a small excavator.

Meanwhile, since the return oil is introduced and filtered from both theupper side and the lower side of the return filter, it is possible towidely use a filtering surface of the filter. Therefore, it is possibleto improve the life of the filter.

The present invention is a construction machine having a working oiltank, the working oil tank comprising a cylindrical filter case having abottom in which a return filter for filtering return oil is housed, thefilter case being provided within the tank main body in which workingoil is stored a plurality of return tubes connected to a filter caseside wall in a state of communicating with the inside of the filtercase, wherein a filter receiving plate is provided in a lower partwithin the filter case with leaving a gap between the filter receivingplate and a filter case bottom wall, the return filter is provided onthe filter receiving plate and at least one of the return tubes isconnected to the filter case side wall on the lower side than the filterreceiving plate.

According to the present invention, since the filter receiving plate isprovided in the lower part within the filter case and the filter isinstalled in a state that the filter is suspended apart from the casebottom wall, it is possible to connect a part of the return tubes to thelower part of the case. That is, it is possible to separately connectthe return tubes to the lower part and the upper part of the filter casewhile avoiding the direct contact of the return oil to the side surfaceof the filter.

Further, it is only necessary to extend the filter case in the heightdirection. There is no need for enlarging the filter case and the tankmain body in the radial direction.

By this, the restrictions on a combination of the return tubes areeased. Therefore, the shape of the return tubes and the connectionstructure are simplified and it is advantageous in terms of themanufacturing property and cost. An effect at this point is remarkablein the small tank mounted in the small excavator. Alternatively, sincethe tank can be downsized, it is possible to reduce a space occupied bythe tank.

Since the return oil can be introduced and filtered from both the upperside and the lower side of the return filter, it is possible to widelyuse the filtering surface of the filter. Therefore, it is possible toimprove the life of the filter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view showing device arrangement of a part ofan upper frame of a hydraulic excavator according to an embodiment ofthe present invention;

FIG. 2 is an enlarged view showing a part of FIG. 1;

FIG. 3 is a sectional view of a working oil tank in FIG. 2;

FIG. 4 is an enlarged view of a part of FIG. 3;

FIG. 5 is a schematic side view of a hydraulic excavator of a preferredexample of the present invention;

FIG. 6 is a view corresponding to FIG. 1 for explaining THE RELATED ART;

FIG. 7 is a view corresponding to FIG. 2 for explaining THE RELATED ART;

FIG. 8 is a sectional view of the working oil tank as THE RELATED ART;and

FIG. 9 is an enlarged sectional view by line IX-IX of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will be given to an embodiment of the present invention onthe basis of FIGS. 1 to 4 and properly with reference to FIGS. 5 to 9for comparative explanation or the like. In the embodiment, a hydraulicexcavator is taken as an example of an object to which the presentinvention is applied.

FIGS. 1 and 2 show device arrangement of a part of an upper frame 12,and correspond to THE RELATED ART shown in FIGS. 6 and 7.

A basic configuration of the embodiment is as follows.

(i) In a rear part of the upper frame 12, are installed an engine 10 anda hydraulic pump 11. On the front side of the engine 10 and thehydraulic pump 11 on the right side, are laterally aligned a controlvalve 13 and a working oil tank 28.(ii) In an end on the right side of the upper frame 12, is openablyattached a guard cover 15 taking the front side as center. By openingthe guard cover 15, maintenance of the control valve 13 and the workingoil tank 28 is performed.(iii) The control valve 13 is formed such that a plurality of mainspools 16 (only one main spool is shown in the figure) are built in onevalve block 17 in a story shape.(iv) The main spools 16 are provided in parallel with the working oiltank 28 (in the longitudinal direction).(v) A pressure compensating spool 18 is provided so as to be orthogonalto the main spool 16, and in a state that a bolt 19 is removed, thespool 18 is attached and detached due to a working space S between thecontrol valve 13 and the working oil tank 28.

Meanwhile, FIGS. 3 and 4 showing a configuration of the working oil tank28 correspond to THE RELATED ART shown in FIGS. 8 and 9.

A basic configuration of the working oil tank 28 is the same as THERELATED ART. The working oil tank 28 is formed such that a cylindricalfilter case 30 having a bottom is attached within a tank main body 29, areturn filter 31 is housed inside thereof, and return oil flowing fromthe hydraulic actuator through a plurality of return tubes 32 isfiltered in the return filter 31, and then returned to the inside of thetank main body 29 by a return pipe 33 installed through a central partof a filter case bottom wall 30 a.

The return filter 31 is disposed on the bottom wall 30 a of the filtercase 30 and held by a push spring 34. In the figure, the referencenumeral 35 denotes a suction filter for filtering feed oil and thereference numeral 36 denotes a suction tube.

In the present embodiment, as a different point from THE RELATED ART,there is firstly a point that a rear half part of a surface (right sidesurface) 29 a of the tank main body 29 of the working oil tank 28opposing to the control valve 13, that is, a part 29 a 1 forming theworking space S which is necessary for attaching and detaching thepressure compensating spool 18 is dented in an inclining surface shapein the direction moving away from the control valve 13 (inward).Therefore, the working space S is formed so as to gradually spreadtowards the rear side.

By this, as understood by comparison with FIG. 7, the working space S isenlarged to the inner side than THE RELATED ART and as shown by animaginary line in FIG. 2, it is possible to attach and detach the bolt19 and the pressure compensating spool 18 in the enlarged working spaceS.

In other words, the rear half part 29 a 1 of the right side surface ofthe tank main body 29 is dented so as to form the working space S whichis necessary and sufficient for attaching and detaching the pressurecompensating spool 18 between the control valve 13 and the working oiltank 28.

By this, without enlarging a gap between the control valve 13 and theworking oil tank 28 and removing the control valve 13, it is possible toeasily and efficiently perform a maintenance work of the pressurecompensating spool 18.

The entire right side surface 29 a of the tank main body 29 is notdented, but only the rear half part 29 a 1 which disturbs the attachmentand the detachment of the pressure compensating spool 18 is dented.Further, the rear half part 29 a 1 is not dented in a concave shape butinclined in the direction moving away from the control valve 13.Therefore, it is possible to minimize a decrease in a capacity of thetank main body 29 due to the dent, while ensuring an extent which isnecessary for the working space S.

Further, in the present embodiment, in order to cover a decreased amountof the tank capacity mentioned above, the working oil tank 28 is formedas follows.

As shown in FIGS. 3 and 4, a filter receiving plate 37 is provided in alower part within the filter case 30 with leaving a gap A (refer to FIG.3) between the filter receiving plate 37 and the filter case bottom wall30 a. The return filter 31 is disposed on the filter receiving plate 37,pushed and held by a push spring 34.

The filter receiving plate 37 is attached to an upper end of the returnpipe 33 passing through the filter case bottle wall 30 a in a state thata central part thereof is passed through by the pipe 33. At least one ofthe return tubes 32 (two return tubes in an example of the figure) isconnected to a lower part of a filter case side wall 30 b on the lowerside than the filter receiving plate 37 (within a range of the gap A).

In other words, a part which is capable of connecting tubes is alsoformed in the lower part of the filter case side wall 30 b, and thereturn tubes 32 are separately connected to an upper part and the lowerpart of the filter case side wall 30 b.

According to the above configuration, in comparison to the case whereall the return tubes 23 are concentrated on and connected to the upperpart of the filter case side wall 21 b in an octopus shape as in THERELATED ART shown in FIGS. 8 and 9, it is possible to shorten aperimeter of the filter case 30 which is necessary for the above tubeconnection.

Therefore, it is possible to reduce the diameter of the filter case 30and hence enlarge an effective capacity of the tank main body 30 so asto cover a dented part of the right side surface 20 a, that is, toensure a necessary tank capacity.

Since the return tubes 32 are separated into the upper side and thelower side, the restrictions on a combination of the return tubes 32 areeased. Therefore, a shape of the return tubes 32 and the connectionstructure are simplified and it is advantageous in terms of amanufacturing property and cost. An effect at this point is remarkablein a small tank mounted in a small excavator.

Meanwhile, since the return oil is introduced and filtered from both theupper side and the lower side of the return filter 31, it is possible towidely use a filtering surface of the filter 31. Therefore, it ispossible to improve the life of the filter 31.

Further, the return pipe 33 originally provided in the tank 28 isslightly extended and the filter receiving plate 37 is supported by thepipe 33. Therefore, there is no need for adding an exclusive member forsupporting the plate 37. Consequently, it is advantageous insimplification of the tank structure and there is no fear that flow ofthe working oil is disturbed within the filter case 30.

Even on the premise of the tank structure of THE RELATED ART shown inFIGS. 8 and 9, it is possible to connect a part of the return tubes 32to the lower part of the filter case side wall 30 b. However by this,the return oil from lower tubes (particularly high pressure oil of amain tube) is brought into direct contact with a side surface of thefilter and hence there is fear that the filtering surface (a filterpaper) is damaged by pressure thereof.

With regard to this point, in the present embodiment, since the filterreceiving plate 37 is provided in the lower part within the filter case30 and the filter 31 is installed in a state that the filter 31 issuspended apart from the case bottom wall 30 a, it is possible toconnect the return tubes 32 to the lower part of the case while avoidingthe direct contact of the return oil with the filter side surface.

In other words, it is possible to separately connect the return tubes 32to the upper side and the lower side without adverse effects that thefilter side surface is damaged by the direct contact of the return oiland a complicated structure of attaching a baffle plate is required inorder to avoid the above damage.

Other Embodiments

(1) A support structure of the filter receiving plate 37 may be changedto other structure such as a structure that a supporting member havingrough mesh is provided between the plate 37 and the filter case bottomwall 30 a.

Alternatively, as is the return structure of THE RELATED ART shown inFIGS. 8 and 9, the return tubes 32 may be separated into the upper sideand the lower side and connected to the filter case 30. In this case,the direct contact of the return oil with the lower side surface of thefilter 31 may be avoided by a known baffle plate.

(2) In accordance with a positional relationship between the working oiltank 28 and the control valve 13, an intermediate part in thelongitudinal direction of the surface 29 a of the tank main body 29opposing to the valve may be dented in a concave shape seen from the topat a part thereof in the valve height direction or a part thereof ofoverall height.(3) In the above embodiment, the description is given to the case wherethe pressure compensating spool 18 and the bolt 19 are to be attachedand detached. However, in the case where a part such as other spoolwhose attachment and detachment are disturbed by the working oil tank 28as well as the spool 18 is provided in the control valve 13, a necessarypart of the tank main body 29 may be dented taking the above part as theobject part.(4) A construction machine provided with the following working oil tankis preferable. The cylindrical filter case 30 having a bottom isattached within the tank main body 29, the return filter 31 is housedinside thereof, and the return oil flowing from the hydraulic actuatorthrough a plurality of the return tubes 32 is filtered in the returnfilter 31, and then returned to the inside of the tank main body 29 bythe return pipe 33 provided in a central part of the filter case bottomwall 30 a.

The reference numeral 34 denotes a push spring for pushing the returnfilter 31 downward, the reference numeral 35 denotes a suction filterfor filtering the feed oil and the reference numeral 36 denotes asuction tube.

In the above working oil tank, the filter receiving plate 37 is providedin the lower part within the filter case 30 with leaving the gap A(refer to FIG. 3) between the filter receiving plate 37 and the filtercase bottom wall 30 a. The return filter 31 is disposed on the filterreceiving plate 37, pushed and held by the push spring 34.

The filter receiving plate 37 is attached to the upper end of the returnpipe 33 passing through the filter case bottle wall 30 a in a state thatthe central part thereof is passed through by the pipe 33. At least oneof the return tubes 32 (two return tubes in an example of the figure) isconnected to the lower part of the filter case side wall 30 b on thelower side than the filter receiving plate 37 (within a range of the gapA).

In other words, the tube connection part in which the return oil is notbrought into direct contact with the filter side surface is also formedin the lower part of the filter case side wall 30 b, and the returntubes 32 are separately connected to the upper part and the lower partof the filter case side wall 30 b.

According to the above configuration, in comparison to the case whereall the return tubes 23 are concentrated on and connected to the upperpart of the filter case side wall 21 b in an octopus shape as in THERELATED ART shown in FIGS. 8 and 9, in the present invention, since thereturn tubes 32 are separated into the upper side and the lower side, itis possible to drastically ease the restrictions on a combination of thereturn tubes, and connect each of the return tubes 32 by selecting aposition to which each of the return tubes 32 is more easily connectedamong the upper side and the lower side. Therefore, it is possible tosimplify the shape of the tubes and the tube structure.

Further, it is only necessary to extend the filter case 30 for the gap Ain the height direction. There is no need for enlarging the filter case30 and the tank main body 29 in the horizontal direction.

Therefore, it is easy to assemble the tank and a manufacturing propertyof the tank is dramatically improved. An effect at this point isparticularly remarkable in a small tank in which a connection area forthe return tubes 32 is limited, and it is highly advantageous for asmall construction machine in which it is difficult to increase size ofthe tank.

Alternatively, it is possible to downsize the tank instead of anassembling property. By this, since a space occupied by the tank isreduced, it is also advantageous for the small construction machine.

Since the return oil is introduced and filtered from both the upper sideand the lower side of the return filter 31, it is possible to widely usethe filtering surface of the filter 31. Therefore, it is possible toimprove the life of the filter 31.

Meanwhile, the return pipe 33 originally provided in the tank isslightly extended and the filter receiving plate 37 is supported by thepipe 33. Therefore, there is no need for adding an exclusive member forsupporting the plate 37. Consequently, it is advantageous insimplification of the tank structure, and there is no fear that the flowof the working oil within the filter case 30 is disturbed.

It should be noted that the support structure of the filter receivingplate 37 may be changed to other structure such as a structure that thesupporting member having rough mesh is provided between the plate 37 andthe filter case bottom wall 30 a.

Although the invention has been described with reference to thepreferred embodiments in the attached figures, it is noted thatequivalents may be employed and substitutions made herein withoutdeparting from the scope of the invention as recited in the claims.

1. A construction machine, comprising: a control valve for controllingan action of a hydraulic actuator; a working oil tank installed in linewith said control valve; a filter case in which a return filter forfiltering return oil is housed, the filter case being provided within atank main body of said working oil tank; and a plurality of return tubesconnected to a side wall of said filter case, wherein a surface of thetank main body of said working oil tank opposing to said control valveis inwardly dented so that between both said working oil tank and saidcontrol valve, is formed a working space which is necessary forattaching and detaching a part of said control valve, while said returntubes are separately connected to the upper side and the lower side ofthe side wall of said filter case.
 2. The construction machine accordingto claim 1, wherein said control valve is provided with a main spool forcontrolling the working direction and speed of the hydraulic actuatorand a pressure compensating spool for compensating a working pressure ofthe hydraulic actuator, the pressure compensating spool being providedat right angles with the main spool, and the surface of the tank mainbody opposing to said control valve is inwardly dented so that betweensaid control valve and said working oil tank, is formed a working spacewhich is necessary for attaching and detaching the pressure compensatingspool.
 3. The construction machine according to claim 1, wherein thesurface of the tank main body opposing to said control valve is dentedin an inclining surface shape in the direction moving away from saidcontrol valve so that a working space gradually spreading in onedirection is formed.
 4. The construction machine according to claim 1,wherein a filter receiving plate is provided in a lower part within saidfilter case of said working oil tank with leaving a gap between thefilter receiving plate and a filter case bottom wall, the return filteris provided on the filter receiving plate, a plurality of said returntubes are separated into the upper side and the lower side and on thelower part, connected to the side wall of said filter case on the lowerside than the filter receiving plate.